The present invention relates to a portable trimmer for cutting grasses, bushes or the like, and more particularly to a portable trimmer in which a brake device for braking the movement of a cutting blade is released in conjunction with a throttle operation of a carburetor.
In portable trimmers for cutting grasses, bushes or the like which are adapted to be driven by an internal combustion engine, such as a compact air-cooled two-stroke cycle gasoline engine, there has been known one type of portable trimmer in which a brake device for braking the movement of a cutting blade is released in conjunction with a throttle operation of a carburetor. For example, such a type of portable trimmer is disclosed in Japanese Patent Laid-Open Publication No. 11-196648. This portable trimmer includes a friction member, and a swingable member for moving the friction member between a brake position, where the friction member is pressed against a clutch drum, and a release position, where the friction member is spaced apart therefrom. Further, the swingable member is adapted to swing in response to the movement of a throttle wire operated by a throttle operation lever for controlling an opening of a throttle valve of a carburetor.
It is an object of the present invention to provide an improved portable trimmer of the type in which a brake device for braking the movement of a cutting blade is released in conjunction with a throttle operation operated by a throttle operation lever and is capable of performing a different operation from the throttle operation by the throttle operation lever.
In order to achieve the above-mentioned object, the present invention provides a portable trimmer which comprises an internal combustion engine, a cutting blade driven by the internal combustion engine, and a centrifugal clutch having a clutch drum for transmitting a driving force of the internal combustion engine to the cutting blade. The portable trimmer further comprises a carburetor having a throttle, a throttle operation lever for opening the throttle, a throttle wire extending between the throttle operation lever and the carburetor, and a swingable member interposed in the throttle wire and being swingable in response to a pulling force of the throttle wire exerted by an operation of the throttle operation lever. The throttle wire includes a first wire portion extending between the throttle operation lever and the swingable member and a second wire portion extending between the swingable member and the carburetor to provide a first operation transmission path for transmitting the movement of the throttle operation lever to the carburetor. Furthermore, the portable trimmer has a brake device for braking the movement of the cutting blade and is released in conjunction with the operation of the throttle operation lever. The brake device includes a friction member which is movable in response to the swing movement of the swingable member between a brake position where the friction member is pressed against the clutch drum, and a release position where the friction member is spaced apart therefrom.
Further, an additional operation lever is provided for performing a different operation from the throttle operation to the portable trimmer. The swingable member is provided with a pulley pivotally attached thereto. The second wire portion extends between the carburetor and the additional operation lever via the pulley to provide a second operation transmission path independent from the first operation transmission path.
The portable trimmer of the present invention includes the first operation transmission path for transmitting the movement of the throttle operation lever to the carburetor to control an opening of a throttle valve of the carburetor, and the second operation transmission path independent of the first operation transmission path, in which the movement of an additional operation lever acts only on the second wire portion. More specifically, in the first operation transmission path, the movement of the throttle operation lever is transmitted to the throttle valve through the first wire portion, the swingable member and the second wire portion to control the opening of the throttle valve and the braking function of the brake device. On the other hand, in the second operation transmission path, the movement of the additional operation lever acts only on the second wire portion extending to the throttle valve via the pulley.
According to the present invention, the portable trimmer has the first operation transmission path for transmitting the movement of the throttle operation lever to control the opening of the throttle valve and the braking function of the brake device, and the second operation transmission path that is independent of the first operation transmission path. Thus, various operational functions of the throttle valve can be added to the portable trimmer.
In an embodiment of the present invention, the second wire portion has a predetermined amount of play for taking up a pulling force which is otherwise applied to the second wire portion in an initial stroke range of the throttle operation leverxe2x80x94the play is set such that the engine is operable at a given intermediate power when the throttle operation lever is at a full stroke position, and the additional operation lever is a power adjusting lever operable to pull the second wire portion to open the carburetor so as to increase a power of the engine higher than the given intermediate power when the throttle operation lever is the full stroke position. This embodiment can facilitate to simplify a structure for adjusting engine power.
In another embodiment of the present invention, the additional operation lever may be an idle-up lever operable to pull the second wire portion so as to partially open the carburetor to increase an idling speed of the engine at the time of starting the engine. This embodiment can facilitate simplifying a structure for providing increased idling speed during warm up of the engine.
In still another embodiment of the present invention, the portable trimmer may further include an intermediate member coupled to the second operation transmission path, and a housing for enclosing at least a part of the engine. In this embodiment, the carburetor is located at a lateral and upward position with respect to the clutch drum when viewed in a direction parallel to a rotational axis of the clutch drum. The swingable member is located above the clutch drum and the intermediate member is disposed between the swingable member and the carburetor. The first wire portion extends vertically to the swingable member in a side interior space of the housing on the opposite side of the carburetor with respect to the clutch drum. Further, the second wire portion has a first end coupled to the carburetor and a second end coupled to the intermediate member. The second wire portion extends laterally from the carburetor in an upper interior space of the housing above the clutch drum and then curves along the pulley and extends to the second end. Thus, a pulling force generated by operating the additional operation lever is transmitted to the second wire portion through the intermediate member. According to this embodiment, various components can be efficiently incorporated in the existing interior space of the engine housing around the clutch drum, which prevents the portable trimmer from increasing in size.